1. Field of the Invention
The present invention relates to a method for producing (meth)acrylic acid, particularly to a method for producing acrylic acid in good yield without any special operation even in an unsteady state which arises at startup or due to some accident or the like.
2. Description of the Related Art
Acrylic acid and methacrylic acid (occasionally referred to as (meth) acrylic acid in this specification and claims) are useful raw materials widely used as raw materials for chemical products, and various production methods thereof are proposed. For example, as methods for producing acrylic acid industrially, a method in which propylene and/or acrolein are subjected to the catalytic gas phase oxidation is commonly used, and a method in which an acrylic acid-containing gas obtained by the catalytic gas phase oxidation method is condensed or absorbed in an absorption liquid to make an acrylic acid-containing solution followed by being subjected to distillation and crystallization to obtain a purified acrylic acid is proposed.
As a purification process, in addition to the method described above, for example, in Japanese Patent Publication No. 2005-15478A, a method in which an acrylic acid-containing gas is brought in contact with an aqueous solution for absorption in an absorption column to obtain an acrylic acid-containing solution, and the acrylic acid-containing solution as a crude acrylic acid is directly subjected to a crystallization process, and a distillate obtained by distilling a residual mother liquid discharged in the crystallization process is circulated in the absorption column is proposed. Such circulation to introduce a high-concentration acrylic acid-containing solution in the crystallization process has an effect of obtaining a highly purified acrylic acid with good absorption efficiency, and even more, the production process is easy and simple.
In Japanese Patent Publication No. 2003-530376A, the purification of acrylic acid using a cleaning column having a function of forcible transport of crystal for the crystallization of acrylic acid is proposed.